1. Field of the Invention
This invention relates to self testing in a computer communication system using wrap-around to send a test message to itself to verify that components of the system are operating properly. More particularly, it relates to swapping destination and sender addresses in the transmit path to preclude the system protocol from discarding the test message in the receive path.
2. Description of the Related Art
The use of wrap-around to test the transmitting and receiving processes in a networking system is well known. Some mechanism for coupling a transmitted signal back into the receiving port of the system is provided, which can be direct hardware coupling or a program-operated switching arrangement.
If the system being tested has a plurality of software and hardware levels and the messages are complex and cast in frames, strict protocols must be adhered to. One of the formal protocols is detecting the address of an incoming message and rejecting the message if it is not addressed to the receiving system.
The system protocols require an external destination address in order for the message to exit via the transmit output ports. The system protocol then detects that the wrapped message is not addressed to the system under test and discards it.
To overcome this problem when using wrap-around to test system components, manual intervention or custom software are used.